Let me make this more explicit, since you clearly didn't get the hint. It's not gendered, you are making it gendered.

I'm just stating a fact that Yoga, by and large, is an activity where female participation massively outnumbers male participation.

You're right that it doesn't _have to_ be gendered but it is - observably so - gendered.

You could also well make an argument that the female body structure lends itself better to flexibility than the male body, due to that elastin and hormones and stuff, so it could well be said that there's a gender-bias built in from the ground up.